District and federal officials are preparing for as many as 4 million people for the inauguration of President-elect Barack Obama, a crowd that would be three or four times larger than previous big events on the Mall.

Only a fraction of those people will be close enough to get a good look at the action. But officials are planning extra JumboTrons at the Mall and along the inaugural parade route so that spectators can feel a part of the historic day.

"The Mall actually may be the best seat in the house. . . . It'll kind of be like the world's biggest stage and auditorium on January 20th," said Mayor Adrian M. Fenty (D), adding that the crowd projections have emerged in briefings conducted by federal and local officials.

All plans are pending approval of the Presidential Inaugural Committee, to be set up by Obama, which determines the size and nature of the inaugural festivities, Fenty said. But District officials have met several times with the Secret Service and other agencies.

The Secret Service is taking the lead in overseeing security and other logistics. Even for a city that has hosted vast throngs for marches, protests, celebrations, funerals and inaugurations, this will be an unprecedented test of planning and resources. The question arises: Can the city handle it? Can millions of people fit downtown?

Or, could there be another Meltdown of '76?

That year, a million spectators were expected on the Mall to celebrate the Bicentennial. Transit officials urged people to take public transportation and promised special service. But there was nothing special about the Fourth of July traffic jam, which stranded cars and buses for hours.

District and federal officials blamed a flawed and smaller mass transit system for the 1976 embarrassment. They expressed confidence that they can handle this January's events. At the same time, they know that Inauguration Day 2009 will be one of a kind.

For example, Fenty said, officials expect people to camp overnight, starting Jan. 19, to get as close as possible to the swearing-in viewing area and parade route.

The next several weeks will be spent figuring out how to change the comprehensive playbook that has been used in the past.

"We have a great blueprint from years past, and we will follow that," the mayor said. "But we will start to make exceptions and deviations because, by everyone's estimation, we will have crowds that will be two, three, maybe even four times as large as the largest inaugural. . . . One of the biggest exceptions would be to open up the Mall."

Officials are talking about opening large sections of the Mall east of the Washington Monument, a space normally used for staging the many components of the inaugural parade, Fenty said. That would make the Mall a viewing area that experts said could accommodate several million people -- significantly more than in the past. Officials have not said where the parade groups will gather instead.

The changes would not affect the 240,000 people who will get free tickets in the space closest to the swearing-in ceremony.

The mayor said visitors will have a difficult choice between getting the best possible views of the swearing-in or the parade.

"The parade route will be completely filled way before the inaugural speech even happens," said Fenty, who was a D.C. Council member in 2005, the most recent inauguration. "That's something people will have to think about, whether they want to see the parade firsthand or see the inaugural swearing-in and speech. You can't do both."

Obama is known for choosing venues where he can address huge crowds. In August in Denver, he accepted the Democratic Party's nomination with a speech before 84,000 at Invesco Field. On election night, about 200,000 jammed Chicago's Grant Park for his victory speech.

"The word we're getting from them, nothing formal yet, is that they want to open this up to as many people as possible," Fenty said. "We will follow their lead."

Peter V. Ueberroth, former chairman of the U.S. Olympic Committee, said that fewer -- not more -- leaders should take charge in a crowd of such size. Ueberroth, who helped guide the 1984 Games in Los Angeles, said security and transportation officials must be closely coordinated, sharing a command headquarters. In this case, the Secret Service will coordinate a unified command center.

It does not appear that the 300 acres of the Mall in the two-mile stretch from the Capitol to the Lincoln Memorial has ever been filled with people, according to Terry Adams, a National Park Service spokesman.

The 1995 Million Man March, which drew about a million people, give or take a few hundred thousand, filled two-thirds of the one-mile section between the Capitol and the Washington Monument, according to photographs taken at the time. Farouk El-Baz, a Boston University expert who analyzed the crowd size, estimated that the entire two-mile stretch is so open that it could hold 3 million people.

"There should be no concern about the number of people. Particularly since this one will be a celebratory gathering. People will be up. They will be pleasant to each other," El-Baz said.

The biggest inaugural crowd appears to be the 1.2 million people who are said to have attended events at the 1965 inauguration of Lyndon B. Johnson, according to police and past news accounts. In those days, the swearing-in was held in the more limited area around the east front of the Capitol, where it had taken place since 1829, according to Beth Hahn of the Senate Historical Office.

It was not until the 1981 inauguration of Ronald Reagan that the swearing-in was moved to the Capitol's west front, where larger audiences could spread onto the Mall.

Faulty mass transit, not space, was the downfall of the July 4, 1976, Bicentennial celebration. Metro ran mostly bus service, which fell into chaos in the traffic jam. Metrorail was in its infancy, with only a 4.6-mile stretch of the Red Line functioning.

Today, with a seasoned and robust subway system, officials are again urging people to take public transit. Once downtown, however, people will face much tighter security than in 1976, as well as world-class traffic problems. Many blocks will be off limits Jan. 20.

"If we can get the doors closed, we will move," Metro spokesman Steven Taubenkibel said. Metro's biggest crowd, recorded July 11, was 854,638 passengers.

The fact that Jan. 20, a federal holiday in the Washington area, falls the day after the Martin Luther King Jr. holiday means that the crowd's arrival might be spread over a four-day weekend. At the same time, the crowd will be packed with out-of-towners and many people attending their first inauguration, creating the potential for confusion.

Those who dare to drive downtown on Inauguration Day will face a monumental parking challenge.

The security zone, which has not been determined, could eat up much of the parking downtown, said Andrew Blair, vice president and secretary of the Washington Parking Association and president of Colonial Parking. The industry is preparing for caravans of buses, he said, adding that the Colonial-run parking lot at Robert F. Kennedy Memorial Stadium will have well over 800 buses.

For those who are making their plans ahead of time, there are 95,000 hotel rooms in the metropolitan area, tourism officials say, in addition to the thousands of basements, spare rooms and sublet homes and apartments that will be available for inauguration-goers. The city is accustomed to hosting 15 million visitors annually.

Security, emergency and logistical crews will be bolstered by about 5,000 members of the military and 4,000 additional officers from 93 law enforcement agencies across the country, officials have said.

Presidential inaugurations aren't just logistical challenges. They shape the start of an administration and provide a chance for the District to shine before a worldwide audience. A major mishap could tarnish the image of the city, the mayor and the organizers, and much is riding on success.